JP5488707B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control device for an internal combustion engine.

  2. Description of the Related Art A fuel injection device for an internal combustion engine is known in which the fuel pressure and the number of fuel injections in one cycle (hereinafter referred to as “the number of fuel injections”) can be changed. Japanese Patent Application Laid-Open No. 2006-336509 discloses a fuel wall surface by performing a control for increasing the fuel pressure at the time of starting the engine as compared with the normal operation after the engine is started and a control for increasing the number of times of fuel injection. A technique for suppressing adhesion is disclosed.

Japanese Unexamined Patent Publication No. 2006-336509 Japanese Unexamined Patent Publication No. 2006-161661

  According to the knowledge of the present inventor, when both the fuel pressure and the number of fuel injections are changed during the operation of the internal combustion engine, the air-fuel ratio is disturbed, resulting in an influence such as torque fluctuation or emission deterioration. There is.

  The present invention has been made in view of the above points, and provides a fuel injection control device for an internal combustion engine capable of suppressing air-fuel ratio disturbance when both the fuel pressure and the number of fuel injections are changed. For the purpose.

In order to achieve the above object, a first invention is a fuel injection control device for an internal combustion engine,
A fuel injector having a fuel injector for injecting fuel into a cylinder or an intake passage of an internal combustion engine, and capable of respectively changing the fuel pressure and the number of fuel injections that is the number of fuel injections in one cycle;
Fuel injection control means for controlling the fuel pressure and the number of times of fuel injection based on the operating state of the internal combustion engine;
With
The fuel injection control means executes timing control for preventing the change timing of the fuel pressure and the change timing of the fuel injection from overlapping when the fuel pressure and the fuel injection frequency need to be changed. And a timing control means.

The second invention is the first invention, wherein
The timing control means is characterized in that, in the timing control, the timing for completing the change of the fuel pressure is delayed with respect to the timing for changing the number of fuel injections.

The third invention is the first or second invention, wherein
The timing control means performs the timing control when increasing the fuel pressure and increasing the number of fuel injections.

According to a fourth invention, in any one of the first to third inventions,
The timing control means executes the timing control when the fuel pressure is reduced and the number of fuel injections is reduced.

According to a fifth invention, in any one of the first to fourth inventions,
The timing control means is characterized in that the change speed of the fuel pressure when the timing control is executed is slower than the change speed of the fuel pressure when the timing control is not executed.

According to a sixth invention, in any one of the first to fifth inventions,
Temperature detecting means for detecting a representative temperature of the internal combustion engine,
In the timing control means, when the representative temperature is low, the time difference between the timing at which the change of the fuel pressure is completed and the timing at which the change of the number of fuel injections is completed is longer than when the representative temperature is high. The timing control is executed as described above.

The seventh invention is the fifth invention, wherein
Temperature detecting means for detecting a representative temperature of the internal combustion engine,
The timing control means executes the timing control so that when the representative temperature is low, the change speed of the fuel pressure is slower than when the representative temperature is high.

  According to the first aspect of the present invention, the timing control for preventing the timing of changing the number of times of fuel injection and the timing of changing the fuel pressure from overlapping each other causes the change in the number of fuel injections to reduce the amount of fuel attached to the wall surface. It is possible to prevent the effect of changing and the effect of changing the fuel pressure from changing the amount of the fuel adhering to the wall at the same time. For this reason, a sudden change in the amount of fuel attached to the wall surface can be prevented. As a result, disturbance in the in-cylinder air-fuel ratio can be suppressed, and adverse effects such as emission deterioration and torque fluctuation can be reliably suppressed.

  According to the second aspect of the present invention, it is possible to more reliably prevent the influence of changing the number of fuel injections from changing the amount of fuel attached to the wall and the influence of changing the fuel pressure from changing the amount of fuel attached to the wall simultaneously. .

  According to the third aspect of the present invention, when the fuel pressure is increased and the number of times of fuel injection is increased, it is possible to suppress a rapid decrease in the amount of wall surface attached fuel by executing the timing control. For this reason, the disturbance of the in-cylinder air-fuel ratio can be reliably suppressed.

  According to the fourth invention, when the fuel pressure is reduced and the number of times of fuel injection is reduced, it is possible to suppress a rapid increase in the amount of fuel attached to the wall surface by executing the timing control. For this reason, the disturbance of the in-cylinder air-fuel ratio can be reliably suppressed.

  According to the fifth aspect of the invention, by changing the fuel pressure change rate when the timing control is executed compared to the fuel pressure change rate when the timing control is not executed, the fuel injection frequency can be changed. It is possible to more reliably prevent the influence of changing the amount of fuel attached to the wall and the influence of changing the fuel pressure from changing the amount of fuel attached to the wall at the same time.

  According to the sixth aspect of the invention, when the temperature of the internal combustion engine is low and the amount of fuel attached to the wall surface is large, the in-cylinder air-fuel ratio is likely to be affected. The time difference from the completion timing can be increased. For this reason, even when the temperature of the internal combustion engine is low, the in-cylinder air-fuel ratio can be more reliably suppressed.

  According to the seventh aspect of the present invention, when the temperature of the internal combustion engine is low and the amount of fuel attached to the wall surface is large, the in-cylinder air-fuel ratio is likely to be affected. The completion timing can be further delayed. For this reason, even when the temperature of the internal combustion engine is low, the in-cylinder air-fuel ratio can be more reliably suppressed.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a time chart for demonstrating the timing control in Embodiment 1 of this invention. It is a time chart for demonstrating the timing control in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

Embodiment 1 FIG.
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system of this embodiment includes a spark ignition type internal combustion engine 10. This internal combustion engine 10 is suitable as a power source for a vehicle. The number of cylinders and the cylinder arrangement of the internal combustion engine 10 are not particularly limited. In FIG. 1, only one cylinder is representatively depicted.

  Each cylinder of the internal combustion engine 10 is provided with a piston 12, an intake valve 14, an exhaust valve 16, a spark plug 18, and a fuel injector 20 that directly injects fuel into the cylinder (combustion chamber). . An intake passage 22 and an exhaust passage 24 are connected to each cylinder.

  The internal combustion engine 10 according to the present embodiment includes a supercharger 26, an intake valve device 44 that drives the intake valve 14, and an exhaust valve device 46 that drives the exhaust valve 16. The supercharger 26 has a compressor 26a and a turbine 26b. The turbine 26 b is disposed in the middle of the exhaust passage 24 and rotates by the energy of the exhaust gas flowing through the exhaust passage 24. The compressor 26 a is disposed in the middle of the intake passage 22, and is compressed by the air in the intake passage 22 by being driven by the turbine 26 b and rotating. However, the present invention is also applicable to an internal combustion engine that does not include a supercharger.

  An air cleaner 28 and an air flow meter 30 for detecting the amount of intake air are installed in the intake passage 22 upstream of the compressor 26a. An intercooler 32, a throttle valve 34, and a surge tank 36 are provided in the intake passage 22 downstream of the compressor 26a. An exhaust purification catalyst 42 for purifying exhaust gas is installed in the exhaust passage 24 downstream of the turbine 26b.

  The system of this embodiment includes an ECU (Electronic Control Unit) 50 that controls the operation of each device of the internal combustion engine 10. In addition to the air flow meter 30, the ECU 50 is electrically connected to a sensor system including sensors described later. The crank angle sensor 38 outputs a signal synchronized with the rotation of the crankshaft of the internal combustion engine 10. The ECU 50 can detect the crank angle and the engine speed based on the output of the crank angle sensor 38. The water temperature sensor 40 detects the cooling water temperature of the internal combustion engine 10. In addition to the above, the sensor system includes various sensors used for controlling the internal combustion engine 10 or the vehicle. In addition to the ignition plug 18, the fuel injector 20, and the throttle valve 34 described above, various devices such as a fuel pump 48 for pressurizing and supplying fuel to the fuel injector 20 are connected to the ECU 50. The fuel pump 48 can change its discharge pressure by, for example, duty ratio control of the drive signal.

  In the present embodiment, the cooling water temperature detected by the water temperature sensor 40 is used as the representative temperature of the internal combustion engine 10, but in the present invention, the temperature of another part of the internal combustion engine 10 may be used as the representative temperature.

  The ECU 50 detects the operating state of the internal combustion engine 10 using a sensor system, and controls the operation by driving each device based on the detection result. For example, the engine speed and the crank angle are detected based on the output of the crank angle sensor 38, and the intake air amount is detected by the air flow meter 30. Further, the fuel injection amount is calculated based on the intake air amount, the engine speed, and the like, and after determining the fuel injection timing, ignition timing, etc. based on the crank angle, the fuel injector 20 and the spark plug 18 are driven.

  According to the fuel injection device of the internal combustion engine 10 of the present embodiment, an air-fuel mixture is formed in the cylinder by directly injecting the fuel from the fuel injector 20 into the cylinder in the intake stroke or the compression stroke, and the ignition of the spark plug 18 is performed. As a trigger, the air-fuel mixture can be burned. Further, the fuel injection device of the present embodiment can arbitrarily control the pressure of the fuel in the fuel injector 20 (hereinafter simply referred to as “fuel pressure”) by changing the discharge pressure of the fuel pump 48. . The higher the fuel pressure, the higher the injection pressure from the fuel injector 20 and the smaller the particle size of the injected fuel spray, and the more easily the fuel is vaporized.

  Furthermore, the fuel injection device according to the present embodiment not only injects the fuel necessary for one cycle from the fuel injector 20 at a time, but also divides the fuel necessary for one cycle from the fuel injector 20 into a plurality of times. Can be injected. In the present specification, the number of fuel injections in one cycle is referred to as “the number of fuel injections”. As the number of fuel injections is increased, the amount of injection per one is reduced, so the length of fuel spray injected from the fuel injector 20 is shortened. As the spray length is shorter, the film thickness of the liquid film (fuel on the wall surface) formed when the fuel spray collides with the wall surface becomes thinner, so the fuel is more easily vaporized.

  In the present embodiment, the operation of the fuel pump 48 and the fuel injector 20 is performed based on a command from the ECU 50 so that the fuel pressure and the number of fuel injections become appropriate values according to the operating state of the internal combustion engine 10. Be controlled. In the present embodiment, the fuel pressure and the number of fuel injections are controlled based on the engine speed and the engine load. However, in the present invention, operating state parameters other than the engine speed and the engine load (for example, The fuel pressure and the number of fuel injections may be controlled in consideration of water temperature, valve timing, EGR rate, and the like. The engine load value can usually be calculated based on the intake air amount and the engine speed, but other parameters (for example, fuel injection amount, required torque, etc.) may be used as the engine load value. Good.

  In the present embodiment, the ECU 50 has a fuel pressure map for calculating or determining the fuel pressure based on the engine operating state and an injection number map for calculating or determining the fuel injection number based on the engine operating state. ECU 50 calculates or determines the fuel pressure and the number of fuel injections by referring to these maps. The fuel pressure map defines the relationship between the two so that the fuel pressure increases as the engine load increases, for example. When the fuel pressure map is set in this way, when the engine load is high, that is, when the fuel injection amount is large, the fuel pressure can be increased to atomize the spray. Even if it exists, vaporization is accelerated | stimulated and a favorable air-fuel | gaseous mixture can be formed. The injection number map defines the relationship between the three so that, for example, the number of fuel injections increases as the engine load increases and the number of fuel injections decreases as the engine speed increases. When the injection frequency map is set in this way, when the engine load is high, that is, when the fuel injection amount is large, the spray length can be shortened by increasing the number of fuel injections. Even if it exists, vaporization is accelerated | stimulated and a favorable air-fuel | gaseous mixture can be formed.

  When the fuel pressure and the number of times of fuel injection are controlled based on the fuel pressure map and the number of times of injection described above, it may be necessary to change both the fuel pressure and the number of times of fuel injection in the transient operation state. For example, when the engine load increases, such as during acceleration, it becomes necessary to increase the fuel pressure and increase the number of fuel injections. Conversely, when the engine load is reduced, it is necessary to reduce the fuel pressure and to reduce the number of fuel injections. The present inventor has found that when both the fuel pressure and the number of fuel injections are changed during the operation of the internal combustion engine 10, the torque fluctuation of the internal combustion engine 10 is likely to occur or the emission is likely to deteriorate. According to the knowledge of the present inventor, this cause is considered as follows.

  Part of the fuel injected from the fuel injector 20 does not vaporize as it is, but adheres to the wall surface. In the case of this embodiment, the wall surface to which the fuel adheres is mainly the inner wall of the cylinder. In addition, fuel can adhere to the wall surfaces of the piston 12, the intake valve 14, the cylinder head, and the like. The fuel adhering to the wall gradually vaporizes. In the steady operation state, the amount of fuel vaporized from the wall surface and the amount of fuel newly adhering to the wall surface become substantially equal, so that the amount of fuel adhered to the wall surface is balanced at a substantially constant value. If the amount of fuel adhering to the wall is kept constant, the amount of fuel contained in the air-fuel mixture in the cylinder becomes equal to the fuel injection amount (fuel injection amount for one cycle). Thus, the air-fuel ratio in the cylinder can be accurately controlled.

  When the fuel pressure is increased, the fuel spray has a small particle size and is easily vaporized. For this reason, when the fuel pressure is increased, the proportion of the injected fuel that adheres to the wall surface decreases. Further, when the number of times of fuel injection is increased, the spray length is shortened, so the proportion of the injected fuel that adheres to the wall surface decreases. When the increase in the fuel pressure and the increase in the number of times of fuel injection are performed simultaneously, the amount of the fuel adhering to the wall surface decreases rapidly due to the overlap of the above two effects. As a result, the amount of fuel contained in the air-fuel mixture in the cylinder becomes larger than the fuel injection amount, and the air-fuel ratio in the cylinder shifts to the rich side.

  On the other hand, when the decrease in the fuel pressure and the decrease in the number of fuel injections are performed simultaneously, the reverse phenomenon occurs and the amount of fuel attached to the wall surface increases rapidly. As a result, the amount of fuel contained in the air-fuel mixture in the cylinder becomes smaller than the fuel injection amount, and the air-fuel ratio in the cylinder shifts to the lean side.

  If both the fuel pressure and the number of fuel injections are changed at the same time, the air-fuel ratio in the cylinder is disturbed for the reasons described above, resulting in torque fluctuations or the emission of the air-fuel ratio deviating from the purification window of the exhaust purification catalyst 42. Or get worse. In order to avoid such adverse effects, in this embodiment, when both the fuel pressure and the number of fuel injections need to be changed, the timing for changing the fuel pressure and the timing for changing the number of fuel injections overlap. It was decided to execute timing control to prevent this. Specifically, as the timing control, control is performed so that the change timing of the fuel pressure is delayed with respect to the change timing of the number of fuel injections. If the timing of changing the number of fuel injections does not overlap with the timing of changing the fuel pressure, the effect of changing the number of fuel injections will change the amount of fuel attached to the wall, and the change in fuel pressure will affect the amount of fuel attached to the wall. Since it is possible to prevent the effects of changing the amount from overlapping at the same time, it is possible to prevent a sudden change in the amount of fuel attached to the wall surface. Therefore, the disturbance of the air-fuel ratio in the cylinder can be suppressed, and adverse effects such as deterioration of emission and torque fluctuation can be reliably suppressed.

  FIG. 2 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. This routine is repeatedly executed every predetermined time. According to the routine shown in FIG. 2, first, the value N0 of the number of fuel injections performed in the current operation is acquired (step 100), and then the value P0 of the fuel pressure performed in the current operation is acquired. (Step 102). The ECU 50 sequentially calculates the appropriate fuel pressure and the number of fuel injections according to the operation state based on the operation state detected by the sensor system, the fuel pressure map, and the injection number map. Here, the latest calculated fuel pressure value is P1, and the latest calculated fuel injection count is N1. In step 104 following step 102, the current fuel pressure P0 acquired in step 102 is compared with the latest fuel pressure calculation value P1. If P1> P0 holds, it can be determined that the fuel pressure needs to be increased. In this case, the current fuel injection number N0 acquired in step 100 is compared with the latest fuel injection number calculation value N1 (step 106). If N1> N0 holds, it can be determined that the number of fuel injections needs to be increased. In this way, when it is determined that there is both a need to increase the fuel pressure and a need to increase the number of fuel injections, timing control is executed (step 108).

  FIG. 3 is a diagram for explaining the timing control of the present embodiment, and is a time chart showing the command value of the number of fuel injections, the command value of the fuel pressure, the in-cylinder air-fuel ratio (A / F), and the engine torque. is there. In the fuel pressure command value, in-cylinder air-fuel ratio, and engine torque in FIG. 3, the thick line indicates the case where the timing control is executed, and the thin line indicates the case where the timing control is not executed as a comparative example. Hereinafter, the timing control of the present embodiment will be further described with reference to FIG. 3, but first, the case of a comparative example in which the timing control is not executed will be described. When timing control is not executed, the command value for the number of fuel injections is increased, and at the same time, the command value for fuel pressure is increased. For this reason, the timing at which the number of times of fuel injection increases and the timing at which the fuel pressure rises overlap (both are changed from the same cycle), the amount of fuel adhering to the wall surface decreases rapidly, and the in-cylinder air-fuel ratio is reduced. Temporarily decreases (enriches). As a result, the engine torque suddenly increases temporarily and torque fluctuations occur. In addition, since the air-fuel ratio in the exhaust purification catalyst 42 is disturbed, the emission is deteriorated.

  On the other hand, when the ECU 50 executes the timing control of the present embodiment, the ECU 50 performs control so as to delay the timing of increasing the fuel pressure command value with respect to the timing of increasing the fuel injection command value. The delay time T, which is the time difference between the timing for increasing the command value for the number of fuel injections and the timing for increasing the command value for the fuel pressure, is, for example, several cycles (for example, about 2 to 10 cycles) in the cycle of the internal combustion engine 10. It can be a corresponding time. The ECU 50 may control the delay time T so as to be a predetermined time, or control the delay time T so that the number of cycles detected by the crank angle sensor 38 reaches a predetermined number of cycles. May be.

  By executing such timing control, the fuel pressure rises with a delay of several cycles from the timing at which the number of fuel injections increases. For this reason, since the rapid decrease in the amount of fuel attached to the wall surface is suppressed, a temporary decrease (riching) of the in-cylinder air-fuel ratio is suppressed. Therefore, changes in the engine torque are suppressed, and torque fluctuations can be avoided reliably. Further, the disturbance of the air-fuel ratio in the exhaust purification catalyst 42 can be suppressed, and the deterioration of emission can be avoided reliably.

  2 and 3, the case where the fuel pressure is increased and the number of times of fuel injection is increased has been described. However, in the present invention, the timing control is also performed when the fuel pressure is decreased and the number of times of fuel injection is decreased. You may make it perform similarly. Further, in the timing control of the present embodiment, the timing for changing the fuel pressure is controlled to be delayed with respect to the timing for changing the number of times of fuel injection, but conversely, for the timing for changing the fuel pressure, You may control to delay the timing which changes the frequency | count of fuel injection.

  The length of the delay time T may be constant, but the length of the delay time T may be changed based on the cooling water temperature detected by the water temperature sensor 40. When the internal combustion engine 10 is at a low temperature, such as immediately after startup, the amount of fuel adhering to the wall surface increases, so that the influence of changes in the number of fuel injections and fuel pressure on the in-cylinder air-fuel ratio tends to increase. For this reason, in order to suppress the disturbance of the in-cylinder air-fuel ratio, it is desired to more reliably prevent the influence of the change in the number of fuel injections and the influence of the change in the fuel pressure from overlapping. In view of this point, in the timing control, it is desirable to control so that the delay time T becomes longer as the coolant temperature is lower. In this way, when the internal combustion engine 10 is at a low temperature, the time difference between the change timing of the number of fuel injections and the change timing of the fuel pressure becomes longer, so that the influence of both can be prevented more reliably. For this reason, even when the internal combustion engine 10 is at a low temperature, the disturbance of the in-cylinder air-fuel ratio can be more reliably suppressed, and the adverse effect can be more reliably suppressed.

In the present invention, the ignition timing control and fuel injection timing control described below may be executed in combination with the timing control.
(Ignition timing control)
The ignition timing control is a control that temporarily corrects the ignition timing in order to suppress a temporary change in torque when the number of fuel injections and the fuel pressure are changed. When the ignition timing is retarded, the torque decreases. For this reason, if the torque temporarily increases when the number of fuel injections and the fuel pressure are changed, the increase in torque can be suppressed by temporarily retarding the ignition timing, and torque fluctuation can be suppressed. It can suppress more reliably.

(Fuel injection timing control)
The rate at which the fuel injected from the fuel injector 20 adheres to the wall surface is also affected by the fuel injection timing. For example, if the fuel is injected from the fuel injector 20 when the piston 12 is near the top dead center, the fuel spray collides with the piston 12, so that the fuel adheres to the piston 12 as well. For this reason, the amount of fuel attached to the wall surface increases. Conversely, when fuel is injected from the fuel injector 20 when the piston 12 is near the bottom dead center, the fuel hardly adheres to the piston 12, so that the amount of fuel attached to the wall surface decreases. Further, if fuel is injected from the fuel injector 20 when the lift of the intake valve 14 is large, the amount of fuel adhering to the intake valve 14 increases, so the amount of fuel attached to the wall surface increases. For this reason, when the fuel injection timing is changed, the amount of fuel attached to the wall surface changes. Therefore, when the number of fuel injections and the fuel pressure are changed, the amount of fuel attached to the wall surface is changed by changing the fuel injection timing in a direction to offset the influence of the change in the number of fuel injections and the fuel pressure on the amount of fuel attached to the wall surface. Can be more reliably suppressed, and as a result, a change in the cylinder air-fuel ratio can be more reliably suppressed. That is, when the fuel pressure is increased by increasing the number of fuel injections, the amount of fuel attached to the wall surface decreases. Therefore, the fuel injection timing is temporarily set in a direction in which the amount of fuel attached to the wall surface increases. It may be corrected manually. Further, when the fuel pressure is decreased by reducing the number of fuel injections, the amount of fuel attached to the wall surface increases, so the fuel injection timing is temporarily set in a direction that reduces the amount of fuel attached to the wall surface. It may be corrected manually.

  In the first embodiment described above, the water temperature sensor 40 corresponds to the “temperature detection means” in the sixth and seventh inventions. Further, the “fuel injection control means” and the “timing control means” in the first to third inventions are realized by the ECU 50 executing the fuel injection control shown in FIGS.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. 4. The description will focus on the differences from the first embodiment described above, and the same matters will be simplified or described. Omitted.

  This embodiment is the same as Embodiment 1 described above except that the method of controlling the fuel pressure in timing control is different. FIG. 4 is a diagram for explaining the timing control of this embodiment, and is a time chart showing the command value of the number of fuel injections, the command value of the fuel pressure, the in-cylinder air-fuel ratio (A / F), and the engine torque. is there.

  When the timing control is not executed, the actual fuel pressure also changes suddenly because the command value of the fuel pressure is suddenly changed. On the other hand, when performing the timing control of the present embodiment, as shown in FIG. 4, the control is performed so that the command value of the fuel pressure is gradually changed. The actual fuel pressure gradually changes following this fuel pressure command value. For this reason, the actual change speed of the fuel pressure is slower than when the timing control is not executed. Therefore, the timing for completing the change of the fuel pressure is later than the timing for completing the change of the number of fuel injections. The slower the change rate of the fuel pressure, the longer the delay time T, which is the time difference between the timing at which the change in the number of fuel injections is completed and the timing at which the change in the fuel pressure is completed.

  By executing such timing control, the fuel pressure is gradually (stepwise) changed, for example, over a period of several cycles. For this reason, since the influence of the change in the fuel pressure on the in-cylinder air-fuel ratio appears gradually (for example, over a period of several cycles), the overlap with the influence of the number of fuel injections is prevented. Therefore, the disturbance of the in-cylinder air-fuel ratio can be reliably suppressed, and the same effect as in the first embodiment can be obtained.

  As described above, when the internal combustion engine 10 is at a low temperature, since the amount of fuel attached to the wall surface is large, the influence of changes in the number of fuel injections and fuel pressure on the in-cylinder air-fuel ratio tends to increase. For this reason, in this embodiment, in timing control, it is desirable to slow down the change speed of fuel pressure, so that cooling water temperature is low. That is, it is desirable to control so that the delay time T becomes longer as the cooling water temperature is lower. In this way, when the internal combustion engine 10 is at a low temperature, the change in the fuel pressure can be made more gradual, so that the disturbance of the in-cylinder air-fuel ratio can be more reliably suppressed.

  In the above-described second embodiment, the ECU 50 executes the fuel injection control shown in FIG. 4 so that the “fuel injection control means” in the first to third inventions and the “timing control means in the fifth invention”. "Is realized.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG. 5. The description will focus on the differences from the above-described embodiments, and the description of the same matters will be simplified or omitted. To do.

  When changing the number of times of fuel injection, the greater the difference (change amount) between the number of times before and after the change, the greater the influence of the change on the in-cylinder air-fuel ratio. For example, the change in the in-cylinder air-fuel ratio is greater when the number of fuel injections is changed from 2 to 4 than when the number is changed from 2 to 3. Also, when the fuel pressure is changed, the influence of the change on the in-cylinder air-fuel ratio is larger as the difference (change amount) in the fuel pressure before and after the change is larger. Therefore, when the number of fuel injections and the fuel pressure are changed, the in-cylinder air-fuel ratio is likely to change as the amount of change increases.

  In view of the above matters, in the timing control of the present embodiment, when the number of fuel injections and the fuel pressure are changed, the delay time T is increased as the amount of change increases. FIG. 5 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. In FIG. 5, the same steps as those of the routine shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  According to the routine shown in FIG. 5, the current fuel pressure P0 is compared with the latest calculated fuel pressure value P1 in step 104. If P1> P0 is satisfied, the fuel pressure change amount ΔP (= P1−P0). ) Is calculated (step 105). Next, in step 106, the current fuel injection number N0 is compared with the latest fuel injection number calculation value N1, and if N1> N0 is satisfied, the injection number change amount ΔN (N1-N0) is calculated (step 1). 110). Subsequently, the delay time T is determined using the fuel pressure change amount ΔP and the injection frequency change amount ΔN as arguments (step 112). In this step 112, the delay time T is set to a longer value as the fuel pressure change amount ΔP is larger, and the delay time T is set to a longer value as the injection number change amount ΔN is larger. Timing control is executed based on the delay time T thus determined (step 114). The fuel pressure control method in this timing control may be any of the methods in the first and second embodiments.

  According to the timing control of the present embodiment described above, when the number of fuel injections and the amount of change in fuel pressure are large, the delay time T can be lengthened as compared with the case where they are small. For this reason, when the amount of change in the number of fuel injections and the fuel pressure is large and the change has a great influence on the in-cylinder air-fuel ratio, the delay time T becomes longer, thereby affecting the effects of the number of fuel injections and the influence of the fuel pressure. Can be more reliably suppressed. For this reason, even if the number of fuel injections and the amount of change in fuel pressure are large, the disturbance of the in-cylinder air-fuel ratio can be more reliably suppressed, and the adverse effects can be more reliably suppressed. In addition, when the number of fuel injections and the amount of change in fuel pressure are small, the delay time T can be shortened. For this reason, it is possible to prevent the change timing of the fuel pressure (or the number of fuel injections) from being delayed more than necessary.

  In each of the embodiments described above, an internal combustion engine including a fuel injection device that directly injects fuel into a cylinder has been described as an example. However, the present invention is directed to fuel injection that injects fuel into an intake passage (intake port). It is also possible to apply to an internal combustion engine provided with the device.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Piston 14 Intake valve 16 Exhaust valve 18 Spark plug 20 Fuel injector 22 Intake passage 24 Exhaust passage 42 Exhaust purification catalyst 50 ECU

Claims (4)

A fuel injector having a fuel injector for injecting fuel into a cylinder or an intake passage of an internal combustion engine, and capable of respectively changing the fuel pressure and the number of fuel injections that is the number of fuel injections in one cycle;
Fuel injection control means for controlling the fuel pressure and the number of times of fuel injection based on the operating state of the internal combustion engine;
With
The fuel injection control means executes timing control for preventing the change timing of the fuel pressure and the change timing of the fuel injection from overlapping when the fuel pressure and the fuel injection frequency need to be changed. Including timing control means for
The timing control means executes the timing control when the fuel pressure is increased and the number of fuel injections is increased, or when the fuel pressure is decreased and the number of fuel injections is decreased .
The fuel injection control device for an internal combustion engine, wherein the timing control means causes the timing for completing the change of the fuel pressure to be delayed with respect to the timing for changing the number of times of fuel injection in the timing control. A fuel injector having a fuel injector for injecting fuel into a cylinder or an intake passage of an internal combustion engine, and capable of respectively changing the fuel pressure and the number of fuel injections that is the number of fuel injections in one cycle;
Fuel injection control means for controlling the fuel pressure and the number of times of fuel injection based on the operating state of the internal combustion engine;
With
The fuel injection control means executes timing control for preventing the change timing of the fuel pressure and the change timing of the fuel injection from overlapping when the fuel pressure and the fuel injection frequency need to be changed. Including timing control means for
The timing control means executes the timing control when the fuel pressure is increased and the number of fuel injections is increased, or when the fuel pressure is decreased and the number of fuel injections is decreased.
It said timing control means is an inner combustion engine you characterized in that as the rate of change of fuel pressure in the case of executing the timing control becomes slow as compared to the rate of change of fuel pressure in the case of not executing the timing control Fuel injection control device. Temperature detecting means for detecting a representative temperature of the internal combustion engine,
The timing control means executes the timing control so that when the representative temperature is low, the change speed of the fuel pressure is slower than when the representative temperature is high. 3. A fuel injection control device for an internal combustion engine according to 2 . A fuel injector having a fuel injector for injecting fuel into a cylinder or an intake passage of an internal combustion engine, and capable of respectively changing the fuel pressure and the number of fuel injections that is the number of fuel injections in one cycle;
Fuel injection control means for controlling the fuel pressure and the number of times of fuel injection based on the operating state of the internal combustion engine;
Temperature detecting means for detecting a representative temperature of the internal combustion engine;
With
The fuel injection control means executes timing control for preventing the change timing of the fuel pressure and the change timing of the fuel injection from overlapping when the fuel pressure and the fuel injection frequency need to be changed. Including timing control means for
The timing control means executes the timing control when the fuel pressure is increased and the number of fuel injections is increased, or when the fuel pressure is decreased and the number of fuel injections is decreased.
In the timing control means, when the representative temperature is low, the time difference between the timing at which the change of the fuel pressure is completed and the timing at which the change of the number of fuel injections is completed is longer than when the representative temperature is high. the fuel injection control apparatus for internal combustion engine and the client performs the timing control so.

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